In parallel, Mr Cameron unmistakably began doing something that is no less alarming for having been long trailed. He is clearing the ground for an election pledge to repeal the Human Rights Act and to withdraw the UK from the European convention on human rights. Tuesday's moves will be seen by many as a Conservative project to remove Britain from the council chambers and common agreements of postwar Europe and to redefine the UK as a deregulatory isolationist offshore financial centre – Singapore with nuclear weapons – within the next three years. The evidence gets stronger by the day.

The first problem with the reshuffle in the European context is the removal of checks and balances that, until now, have kept Conservative Euroscepticism on a relatively tight rein. The replacement of William Hague, a big figure and a pragmatic foreign secretary, by Philip Hammond, a lesser successor who has indicated that as things stand he would vote to leave the EU, tilts the balance towards an isolationist approach. The exit of Mr Clarke removes the only Tory round the cabinet table with the instinct to challenge the drift out into the Atlantic. Although the departure of the Eurosceptic Owen Paterson and the vanity of Liam Fox's refusal to return to office in a subordinate position are some comfort, it may only be a matter of time before the interplay of Tory party politics begins to remorselessly raise the EU renegotiation bar much higher than would have been allowed in the Hague and Clarke era.

The second problem is the momentum towards abandoning the convention, which would leave Britain alone with Belarus as non-signatory European nations. The sacked attorney general Dominic Grieve, backed by Mr Clarke and the Lib Dems, possessed both the principles and the clout to see that the UK's reputation, and its standing as a critic of human rights abuses elsewhere, including Russia, would be disastrously undermined by abandoning the convention. Mr Grieve's departure, plus Damian Green's exit from the Home Office, removes all that. It opens the way to the coarser anti-rights populism promoted by Chris Grayling and indulged by Mr Cameron. The prime minister now has a much freer hand to pursue this policy.

Lord Hill's nomination as the next EU commissioner may seem an oddly modest decision in these more dramatic contexts. Mr Cameron has selected a good negotiator, a practical administrator and an effective operator. But he has done this because Nick Clegg, under the coalition code, had the power to stop a more confrontational or higher-profile choice.

If Lord Hill does his job in Jean-Claude Juncker's new European commission, he may help to provide Mr Cameron – if he is still prime minister – with some of the reforms that could enable him to recommend a yes vote in a 2017 referendum. The fact that Mr Cameron is playing hardball now may mask a readiness to compromise later.

If nothing else, Tuesday exposed the emptiness of complaints that there is no difference between our political parties. The difference revealed last night is enormous. The signals from Mr Cameron add up to a real and present danger which, carried to their conclusion, could redefine this country's place in the world for the worse, for years to come.